Top Most LINQ Interview Questions

1. What is LINQ?

It stands for Language Integrated Query. LINQ is collection of standard query operators that provides the query facilities into .NET framework language like C# , VB.NET.

2. Why can not datareader by returned from a Web Services Method?

Because, it is not serializable

3. What is the extension of the file, when LINQ to SQL is used?

The extension of the file is .dbml

4. How LINQ is beneficial than Stored Procedures?

There are couple of advantage of LINQ over stored procedures.

1. Debugging – It is really very hard to debug the Stored procedure but as LINQ is part of .NET, you can use visual studio’s debugger to debug the queries.
2. Deployment – With stored procedures, we need to provide an additional script for stored procedures but with LINQ everything gets complied into single DLL hence deployment becomes easy.
3. Type Safety – LINQ is type safe, so queries errors are type checked at compile time. It is really good to encounter an error when compiling rather than runtime exception!

5. What is a Lambda expression?

A Lambda expression is nothing but an Anonymous Function, can contain expressions and statements. Lambda expressions can be used mostly to create delegates or expression tree types. Lambda expression uses lambda operator => and read as ‘goes to’ operator.
Left side of this operator specifies the input parameters and contains the expression or statement block at the right side.

Example: myExp = myExp/10;

Now, let see how we can assign the above to a delegate and create an expression tree:

delegate int myDel(int intMyNum);
static void Main(string[] args)
{
//assign lambda expression to a delegate:
myDel myDelegate = myExp => myExp / 10;
int intRes = myDelegate(110);
Console.WriteLine(“Output {0}”, intRes);
Console.ReadLine();

//Create an expression tree type
//This needs System.Linq.Expressions
Expression myExpDel = myExp => myExp /10;
}

Note:

The => operator has the same precedence as assignment (=) and is right-associative.
Lambdas are used in method-based LINQ queries as arguments to standard query operator methods such as Where.

6. What is the LINQ file extension that interacts with Code Behind objects.

its .dbml

7. Why Select clause comes after from clause in LINQ?

The reason is, LINQ is used with C# or other programming languages, which requires all the variables to be declared first. From clause of LINQ query just defines the range or conditions to select records. So that’s why from clause must appear before Select in LINQ.